From: Tomas Krizek <tomas.krizek@nic.cz>
Date: Tue, 28 Jan 2020 14:38:37 +0000 (+0100)
Subject: doc/cache: add note explaining cache size choice
X-Git-Tag: v5.0.1~3^2~1
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=dbbb0b73eae4aff8b4acc4e40753eab84fb52180;p=thirdparty%2Fknot-resolver.git

doc/cache: add note explaining cache size choice
---

diff --git a/ci/respdiff/kresd.config b/ci/respdiff/kresd.config
index 7da2eaa4b..583822b1e 100644
--- a/ci/respdiff/kresd.config
+++ b/ci/respdiff/kresd.config
@@ -7,9 +7,6 @@ net.ipv6=false
 -- Auto-maintain root TA
 trust_anchors.add_file('.local/etc/knot-resolver/root.keys')
 
--- Large cache size, so we don't need to flush often
--- This can be larger than available RAM, least frequently accessed
--- records will be paged out
 cache.size = 1024 * MB
 
 -- Load Useful modules
diff --git a/daemon/bindings/cache.rst b/daemon/bindings/cache.rst
index c14cbcfd2..eeadb6fcf 100644
--- a/daemon/bindings/cache.rst
+++ b/daemon/bindings/cache.rst
@@ -20,6 +20,10 @@ For personal and small office use-cases cache size around 100 MB is more than en
 For large deployments we recommend to run Knot Resolver on a dedicated machine,
 and to allocate 90% of machine's free memory for resolver's cache.
 
+.. note:: Choosing a cache size that can fit into RAM is important even if the
+   cache is stored on disk (default). Otherwise, the extra I/O caused by disk
+   access for missing pages can cause performance issues.
+
 For example, imagine you have a machine with 16 GB of memory.
 After machine restart you use command ``free -m`` to determine
 amount of free memory (without swap):
diff --git a/etc/config/config.cluster b/etc/config/config.cluster
index 1fbc0b84d..d8c6c7023 100644
--- a/etc/config/config.cluster
+++ b/etc/config/config.cluster
@@ -11,10 +11,8 @@ net.listen('::1', 53, { kind = 'dns'})
 net.listen('127.0.0.1', 853, { kind = 'tls' })
 net.listen('::1', 853, { kind = 'tls' })
 
--- Large cache size, so we don't need to flush ever
--- This can be larger than available RAM, least frequently accessed
--- records will be paged out as long as there's enough disk space to back it
-cache.size = 100 * GB
+-- Refer to manual for optimal cache size
+cache.size = 16 * GB
 
 -- Load Useful modules
 modules = {
diff --git a/etc/config/config.isp b/etc/config/config.isp
index bf9d65c84..7d00131b3 100644
--- a/etc/config/config.isp
+++ b/etc/config/config.isp
@@ -8,9 +8,7 @@ net.listen('::1', 53, { kind = 'dns'})
 net.listen('127.0.0.1', 853, { kind = 'tls' })
 net.listen('::1', 853, { kind = 'tls' })
 
--- Large cache size, so we don't need to flush often
--- This can be larger than available RAM, least frequently accessed
--- records will be paged out
+-- Refer to manual for optimal cache size
 cache.size = 4 * GB
 
 -- load modules
diff --git a/etc/config/config.splitview b/etc/config/config.splitview
index 04b47edb6..f2b7cd055 100644
--- a/etc/config/config.splitview
+++ b/etc/config/config.splitview
@@ -22,9 +22,7 @@ modules = {
 	dns64 = 'fe80::21b:77ff:0:0',
 }
 
--- Large cache size, so we don't need to flush often
--- This can be larger than available RAM, least frequently accessed
--- records will be paged out
+-- Refer to manual for optimal cache size
 cache.size = 4 * GB
 
 -- Forward everything below `company.cz` to `192.168.1.3`